Sheet metal lower blade for the cutter head of dry shaving apparatus



May 6, 1958 G. HEYEK 2,833,033

sum METAL LOWER BLADE FOR THE CUTTER HEAD OF DRY SHAVING APPARATUS Filed Nov. 50, 1954 \l A El F/g. 4

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BY WM 696 Wmmw ATTORNEYS SHEET METAL LOWER BLADE FOR THE CUTTER HEAD OF DRY SHAVING APPARATUS Gerhard Heyek, Graz, Styria, Austria Application November 30, 1954, Serial No. 472,083 Claims priority, application Austria December 17, 1953 7 Claims. (CI. 30-43) The invention relates to a lower blade for the cutter head of dry shaving apparatus in which the lower blade has a convex cylindrical cutting surface and is reciprocated on the concave inside of a shear plate or upper blade which is also cylindrically curved and formed with apertures for penetration by the hair. In dry shaving apparatus of that type the movement of the lower blade is effected with a high periodicity, e. g. with 6000 cycles per second. For this reason it is essential to keep the mass of the lower blade as small as possible in order to avoid undesirable vibration and noise. The reduction of the mass of the lower blade has the additional ad vantage that the drive mechanism, which imparts the reciprocating motion to the blade and which in most cases comprises an eccentric or crank drive; is stressed and worn to a minor degree and for this reason can be made in a weaker design so that the entire apparatus can be manufactured at lower cost and yet have greater durability.

It is an object of the invention to provide a lower blade of the type described, which combines satisfactory rigidity with light weight and which can be manufactured at low cost. 7

With these and other objects in mind the invention provides a lower blade for a cutter head of dry shaving apparatus comprising drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having a convex cylindrical outside surface formed with a plurality of cuts extending transversely of the generatrix of said surface and with an outwardly bent sheet metal flange portion at least on one side of each of said cuts, each of said outwardly bent flange portions having a free longitudinal edge, said free edges being ground according to a common cylindrical surface to form cutting edges.

The invention further provides a lower blade for a cutter head of dry shaving apparatus comprising drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having a convex cylindrical outside surface formedflwith a plurality of cutting edges extending in a common cylindrical surface transversely of the generatrix of said outside cylindrical surface of the blade body, and two longitudinal margins having connected thereto a platedisposed on the inside of said blade body and provided with means engageable by said drive means for reciprocating said blade.

As will be explained hereinafter, lower blades of that type can 'be rnanufactured in a particularly simple manner and are very light in weight so that vibration and wear are avoided to a high degree inlthe use of the dry shaving apparatus. Depending on whether sheet metal flange portions are bent outwardly on one or both sides of the cuts, .thelands. remaining between the cuts are of angle or channel section. Alternatively inwardly bent sheet metal flange portions may be provided on one side and outwardly bent sheet metal'fiange portions may be provided on the other side of the cuts; in that case said lands are of Z-shaped section. All these land sec-' tions provide for a high rigidity of the lower blade.

Other features and advantages of the invention will become apparent from the following description of il- 5. lustrative embodiments, having reference to the drawing.

Fig. 1 is a perspective view of a lower blade according to the invention. Figs. 2 and 3 respectively are a transverse section view taken on line IIII and a longitudinal sectional view taken on line III-III in Fig. 1. Figs. 4 and 5 are longitudinal sectional views similar to Fig. 3 and showing modified embodiments of the invention. Finally, Fig. 6 is a transverse sectional view similar to Fig. 2 and showing an additional embodiment of the invention. 7

The lower blade B shown in Fig. 1 comprises a body 1 of sheet steel, preferably sheet special steel, which is cylindrically curved to have substantially the form of an oblong segment of the periphery of a cylinder. Closely spaced cuts 2 extending transversely of the generatrix of said cylinder are formed in that body. In the embodiment shown, sheet metal flange portions 3 are bent outwardly on both sides of each of said cuts. The cuts 2 and sheet metal flanges 3 are formed suitably in a single stamping operation, in which the body ll is cut open in its peripheral direction at the center of the slots 2 and the two sheet metal edges adjoining the out are bent outwardly at right angles to the convex side of the body 1 to form the flanges 3.

The free outer longitudinal edge surfaces of the sheet metal flanges 3, having a rough profile 4 after the cutting and stamping operations, are surface ground as shown in Fig. 2 along a common cylindrical surface 5. This ensures a snug engagement of the lower blade on the shear plate and on the other hand leads to the formation of sharp cutting edges 6 on both sides of each flange 3. Only little grinding work is required because the grinding operation is restricted to the relatively narrow edge surfaces 4 of the lands. Thus the lower blade described can be manufactured at low cost.

When sheet metal flange portions 3 are bent outwardly V on both sides of the cuts 2 the lower blade will assume the longitudinal sectional shape shown in Fig. 3, in which the lands 11 remaining between the cuts 2 are of channel section. The troughs formed by said chanel sections may involve difficulties as regards cleaning the cutter head or keeping it clean, because theymay collect dust from shaving which can be removed only with difliculty. In the embodiment shown in Fig. 4 that difliculty is avoided byforming outwardly bent sheet metal flange portions 3 only on one side of the cuts 2. Thus the lands are of angle section and the dust from shaving can enter unobstructedlythrough the gaps between the lands the convex internal space of the lower blade. I

Finally, Fig. 5 represents another embodiment, in which sheet metal portions 3 are bent outwardly on one side, of the cuts and sheet metal portions 7 arebent inwardly on the other side. Thus the lands between the cuts'2 have a z-shaped profile. That embodiment has the same advantage as that shown in Fig. 4 but'provides for a higher rigidity of the blade owing to the inwardlydirected is fixed with its flanges to the longitudinal margins of the blade body 1 by spotwelding, riveting or the like and which. carries the-mean's for. engagement by the drive" mechanism for the lower blade, For instance, that plate 3 may have a central transverse slot 12 which receives 0 an eccentric rotary pin 13, as indicated in Fig. 6.

The manufacture of the blade described and the fixation Eatented May 6, 1958 7 into 7 of the lower plate 8 are simplified when according to Fig. 6 the cylindrically curved sheet forming the blade body is bent along both longitudinal edges first outwardly. and then downwardly to form outwardly of said cuts distinct corners 9, which pass over into substantially parallel holding flanges or margins 10. Due 'to the bending of the body 1 at 9 a clean cut is provided for during the punching of the cuts 2 and in the operation of bending the flange portions 3 on the sides of the cuts because the engagement of the cutting and stamping tools takes place substantially at right angles. Further, the fixation of the plate 8 is facilitated because the same can be passed into the inner space of the concave body 1 until it engages the corner portion 9, and can then be welded or riveted precisely to the side flanges 10 thereof.

It is obvious that the cuts 2 need not extend in planes which are at right angles to the longitudinal axis of the blade body but maybe inclined, e. g. theymay form parts of a helix. The cylindrically curved blade body may have the cross-sectional shape of an arc of a circle, of a parabola, a caternary, or the like.

The end portions 11 of the cylindrical blade body serve only for holding it during the bending and stamping operations. As is shown on the right in Figs. 3-5 they are cut off at a later stage of the manufacture of the blade so that the entire length of the blade is available for shaving.

I claim:

1. A cutter head of dry shaving apparatus comprising a lower blade, drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having a convex cylindrical outside surface formed with a plurality of spaced cuts extending transversely of the generatrix of said surface and leaving land portions within said surface between said cuts, and a sheet metal flange portion projecting substantially perpendicularly to and outwardly from said surface at least on one side of each of said land portions, each of said outwardly projecting flange portions having a free longitudinal edge of substantially rectangular cross-section, said free edges lying in a common imaginary cylindrical surface to form cutting edges.

2. A cutter head of dry'shaving apparatus comprising a lower blade, drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having a convex cylindrical outside surface formed with a plurality of spaced cuts extending transversely of the generatrix of said surface and leaving land portions within said surface between said cuts, and a sheet metal flange portion projecting substantially perpendicularly to and outwardly from said surface on both sides of each of said land portions to form channel-section lands between said cuts, each of said outwardly projecting flange portions having a free longitudinal edge of substantially rectangular cross-section, said free edges lying in a common imaginary cylindrical surface to form cutting edges.

3. A cutter head of dry shaving apparatus comprising a lower blade, drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having'a convex cylindrical outside surface formed with a plurality of spaced cuts extending transversely of the generatrix of said surface and leaving land portions within said surface between said cuts, and a sheet metal flange portion projecting substantially perpendicularly to and outwardly from said surface only on one side of each of said land portions to form angle-section lands between said cuts, each of said outwardly projecting flange portions having a free longitudinal edge of substantially rectangular cross-section, said free edges lying in a common imaginary cylindrical surface to form cutting edges.

4. A cutter head of dry shaving apparatus comprising a lower blade, drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having a convex cylindrical outside surface formed with a plurality of spaced cuts extending transversely of the generatrix of said surface and leaving land portions within said surfacebetween said cuts, and a sheet metal flange portion projecting substantially perpendicularly to and outwardly from said surface on one side and with a sheet metal flange portion projecting inwardly from said surface on the other side of each of said land portions to form lands of Z-shaped section between said cuts, each of said outwardly projecting flange portions having a free longitudinal edge of substantially rectangular cross-section, said free edges lying in a common imaginary cylindrical surface to form cutting'edges.

5. A cutter head of dry shaving apparatus comprising a lower blade, drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having a convex cylindrical outside surface formed with a plurality of spaced cuts extending transversely of the generatrix of said surface and leaving land portions within said surface between said cuts, and a sheet metal flange portion projecting substantially perpendicularly to and outwardly from said surface at least on one side of each of said land portions, each of said outwardly projecting flange portions having a free longitudinal edge of substantially rectangular cross-section, said free edges lying in a common imaginary cylindrical surface to form cutting edges, said blade body being further formed with two distinct longitudinal corners outwardly of said cuts, and with mutually substantially parallel holding flanges adjoining said corners.

6. A cutter head of dry shaving apparatus comprising a lower blade, drive means for reciprocating said lower blade, which blade comprises a sheet metal blade body having a convex cylindrical outside surface formed with a plurality of cutting edges extending in a common cylindrical surface transversely of the generatrix of the out side cylindrical surface of the blade body, said blade body being further formed with two distinct longitudinal corners outwardly of said cutting edges and with mutually substantially parallel holding flanges adjoining said corners, said blade further comprising a plate disposed on the inside of said blade body and provided with means engageable by said drive means for reciprocating said blade body, said plate being formed with two longitudinal flanges connected to the holding flanges of the blade body and engaging said corners.

7. A lower blade for a cutter head of dry shaving apparatus comprising a sheet metal blade body having a convex cylindrical outside surface formed with a plurality of relatively spaced cuts extending transversely of the generatrix of said surface and leaving laud portions within said surface between said cuts, a sheet metal flange portionhaving parallel plane faces projecting substantially perpendicularly to and outwardly from said surface in a plane radial to said generatrix on one side of said land portion, each of said flange portions having a free longitudinal edge disposed normally to each of the plane faces of the sheet metal from which it is formed, said free edges lying on a common imaginary cylindrical surface.

' References Cited in the file of this patent UNITED STATES PATENTS Lonne Iuly 27, 1948 

